The planocentric gear unit (conventional name in foreign countries) has advantages of small volume, light weight, low noise, low mesh linear velocity, small contact stress and so on, in the current situation of our country, the planocentric gear unit and the cycloidal pin wheel reducer commonly occupy the main market of small and medium power with large speed ratio; although it has marry structure types, the common disadvantage is unsatisfactory transmission efficiency (including the cycloidal pin wheel type). The SCC series planocentric gear units developed by our inventor was authenticated by Yangzhou City Science and Technology Commission on 29, Aug. 1985, and SCCII series plane centric gear units was authenticated by Jiangsu Science and Technology Commission in 1988, and our utility model ZL88211046.2 A Rolling Hinge Pin Bushing Output Mechanism (Refer to the copy of the authentication certificate) was used, however the efficiency was still not ideal enough, especially the efficiency in high power and super-high power transmissions was a very sensitive problem; taking a 10000 KW increasing gear/reducing gear for example, 1% efficiency means 100 KW energy consumptions or incomes; at present 1000˜2000 KW wind generator increasing gears unit manufactured in our country mostly adopt level 2 set NOW planetary unit comprising external gears, they have high machining precision and large tooth profile contact stress (as high as 80˜100 kg/mm2 or higher), low contact stress of the corresponding planocentric gear trains is about 8˜10/mm2 or lower, the noises thereof is generally below 70 dB, but the transmission efficiency thereof fails to rank in thousand KW grade, and the noises of the corresponding NGW planetary gear trains are about 80 dB.
In the prior art, speed reducing gear units for ships, in particular for large ships mostly adopt external mesh reducing gears, which usually use high/lower speed diesel engines or gas turbines as the motive power, the speed ratio of the reducing gears is between 4˜8; however when high speed diesel engines or gas turbines are used as the motive power (n≈3000˜6000 r.p.m), the weight of the onboard prime motor can be reduced greatly, the speed ratio of the reducing gear can be increased to 30 times or higher correspondingly; comparatively speaking, if an external mesh transmission is used, the structure is very huge.